Sister Bay, WI has a population of 710 and is the 17,385th largest city in the United States. The population density is 275 per sq mi which is 215% higher than the Wisconsin average and 204% higher than the national average. The median age in Sister Bay is 65 which is approximately 67% higher than the Wisconsin average of 39. In Sister Bay, 74% of the population over 15 years of age are married, 96% speak English and 1% speak Spanish. 46% of Sister Bay residents were born in Wisconsin, 47% were born out of state, 1% were born outside of the United States and 5% were foreign born.